H ion pumping across the mitochondrial membrane is an integral part of the overall process of oxidative phosphorylation in mitochondria. There is evidence for two types of H ion gradient, and one associated with the utilization of the gradient energy for ATP synthesis. The principal aim of the project is to study the detailed mechanism of H ion translocation associated with the latter system. H ion translocation mediated by the mitochondrial DCCD-binding proteolipid will be studied as well as its regulation by other hydrophobic membrane proteins, such as the oligomycin sensitivity conferring protein (or OSCP), F6, coupling factor B and the uncoupler binding protein.